You know how every couple of years, comic book companies will do a hard reset on their characters so they won’t have to keep up with complicated, alienating canon? That might be a good starting point.
The Book of Enoch contains several sections, including a portion called the Book of the Watchers. Here, the author details Enoch’s vision of heaven and the fall of a subsect of angels who would go on to interbreed with human beings, creating a race called the Nephilim: supernatural, man-eating, cannibalistic, vampiric giants. It was all very hat-on-a-hat. Other additions included the angel Azazel teaching humans how to make swords, God’s orders to have the rebelling angels bound and imprisoned, and a long-winded explanation for why the Great Flood was a pretty cool idea.
Needless to say, there were a lot of big thoughts and at least a couple of hot screenplay concepts in there. But grand ideas get you grand opposition, and early theologians branded some of Enoch’s ideas as heretical. According to the Encyclopedia Britannica, of particular concern were prophecies involving the birth of a messiah, which didn’t sit well with the Jewish community. That, surprisingly, seems to be what got the ball rolling on ditching the texts, not the inclusion of blood-sucking Kaiju monsters.